Effects of bilayer number and thickness ratio on structure and properties of (Cr, N)-DLC/DLC multilayer films

(Cr, N)-DLC/DLC multilayer films with different bilayer numbers and thickness ratios were prepared on cemented carbides and silicon wafers by cathodic vacuum arc technology. Surface and cross-section morphologies of multilayer films were observed by scanning electron microscope. Roughness, hardness, adhesion strength, friction coefficient and wear rates of the deposited films were investigated by surface profiler, nanoindentor, scratch tester, and ball-on-disk tribometer, respectively. Alternating stress field from adjacent sublayers benefited the mechanical properties while macroparticles piercing through interfaces between sublayers provided passages for cracks propagation and deteriorated films' mechanical properties. As bilayer numbers varied from 10 to 20 average friction coefficient and roughness of multilayer films had the same changing trend and wear rates increased linearly from 2.45 × 10^-7 mm³/Nm to 3.81 × 10^-7 mm³/Nm. Improving proportion of (Cr, N)-DLC layer in multilayer films increased quantity of macroparticles, leading to the rise of multilayer films' roughness, average friction coefficient and wear rates.